It should never be relied upon for specific medical advice. Some examples of nitrates are nitroglycerin Nitro-Dur, Nitrostat, others , isosorbide mononitrate Monoket and isosorbide dinitrate Bidil. And, according to studies , it is the most effective one, too. Inhibitors like Tadalafil stop the arrival of PDE5, which means that cGMP, which loosens up smooth muscles and keeps up with blood vessels, can tackle its work easily. Does Tadalafil have fewer side effects than Sildenafil? These medicines are called PDE5 inhibitors.The four main medicines taken by mouth for erectile dysfunction are: Avanafil (Stendra). Sildenafil (Viagra). Tadalafil (Cialis). Vardenafil. These medicines are called . Cialis usually takes about 30 minutes to take effect with sexual stimulation and its effect lasts for up to 36 hours, which is why it is sometimes referred to as a . 4th May Manual Health Centre. In 30 seconds How long does Viagra take to work? The effects of Sildenafil – the active ingredient in the little blue pill – can usually be felt .